Which artifact is produced when the ultrasound beam refracts at an oblique interface?

Which artifact is produced when the ultrasound beam refracts at an oblique interface?

• A. Shadowing
• B. Refraction artifact
• C. Ringing
• D. Aliasing

Answer: (B)

When the ultrasound beam meets an interface at an angle and the tissues on either side have different speeds of sound, the beam bends. This bending, or refraction, causes echoes to be mapped to locations that don’t match their true positions, leading to a misregistration on the image. The result is the refraction artifact, which can show a structure shifted laterally or even appear as a duplicate image along the side. Other artifacts have different causes: shadowing happens when an object strongly attenuates the beam and blocks signals behind it; ringing comes from the transducer pulse continuing to oscillate and producing extra echoes near a strong reflector; aliasing occurs with Doppler when the flow signal exceeds the system’s sampling limits.

When the ultrasound beam meets an interface at an angle and the tissues on either side have different speeds of sound, the beam bends. This bending, or refraction, causes echoes to be mapped to locations that don’t match their true positions, leading to a misregistration on the image. The result is the refraction artifact, which can show a structure shifted laterally or even appear as a duplicate image along the side.

Other artifacts have different causes: shadowing happens when an object strongly attenuates the beam and blocks signals behind it; ringing comes from the transducer pulse continuing to oscillate and producing extra echoes near a strong reflector; aliasing occurs with Doppler when the flow signal exceeds the system’s sampling limits.